It is necessary upon removing coal from a mine or strip pit to further process the coal before use by breaking the coal and sorting it into certain sizes and removing rocks, shale or other impurities therefrom. Depending upon the final use for which the coal is intended and the type and hardness of the particular coal being mined, the coal is broken and separated into predetermined size particles. Two inch size particles is a common size for many burning applications.
This crushing and splitting of the coal has been performed by various types of equipment such as a rotary roll crusher in which coal passes between and is crushed by counter-rotating rolls and then discharged into a chute or conveyor for subsequent shipment. Such roll crushers have the disadvantage in that everything including coal and other impurities must go through the crusher rolls and are broken into smaller particles. It is preferable that impurities be removed and not crushed and transported with the coal. Another type of prior art crusher or breaker is a rotary breaker which consists of a large hollow rotating drum having a plurality of holes and baffles inside which will break the coal as it is tumbled wirhin the drum.
Although these breakers perform satisfactorily, they require a considerable amount of energy for rotating the drum or crusher rolls. Furthermore, it is difficult to change the setting for the size coal desired. Also it is difficult to conform the breaking force with the hardness of the particular seam of coal being broken by the equipment.
These known crushers usually are located at a coal wash plant which may be located some distance from the mine or pit, requiring the coal together with the impurities to be transported to the processing site with the refuse or removed impurities being returned to the original site for disposal. All of these hauling and processing operations increase the cost of processing the coal.
Several types of coal breakers use rotors which propel the coal against impact surfaces for breaking the coal into smaller particles. Examples of these types of breakers are shown in U.S. Pat. Nos. 2,119,850 and 2,192,606. Although these breakers perform satisfactorily, they require a relatively large motor and increased power because of the heavy structural members since the rotor changes the direction of the coal or material being broken after being struck with the rotor blades. Also the rotor blades perform some of the crushing or breaking action instead of merely propelling the coal particles and increasing the speed thereof for impact crushing against a surface. These types of rotary crushers also have the disadvantage of not removing the coal particles as soon as possible after being reduced to the desired size. The coal and sized particles will remain in the crusher for a longer period of time than necessary resulting in the particles being further reduced in size which results in fines or dust being created which may be too small for use and sale.
Accordingly, there is a need for an improved coal breaker and sorter which eliminates the above problems and satisfies needs existing in the art.